Size makes 17,500-pounder king of crocs

Paleontologist rebuilds monster

It's lucky for Steve Irwin, television's intrepid crocodile hunter, that the "Super Croc" fossil recovered by University of Chicago paleontologist Paul Sereno has been extinct for millions of years.

At 40 feet long and 17,500 pounds, Super Croc was so big and mean when it lived 110 million years ago that it exploded out of rivers to grab and eat dinosaurs. It had a 6-foot-long jaw filled with more than 100 pointed teeth and an enormous, toilet bowl-sized sinus cavity at the tip of its nose, all the better to smell with.

Sereno describes Sarcosuchus imperator, which he nicknamed Super Croc, and other African fossils he unearthed last year in Friday's edition of the research journal Science.

Although French paleontologists were the first to describe and name Sarcosuchus in 1966, they found only partial remains. Last year Sereno led an expedition to the same fossil-rich area of Niger to look for dinosaurs and discovered the complete skull of an adult Sarcosuchus, plus the ribs, spines and tails of several juveniles.

Based on those finds, Sereno was able to describe Super Croc in detail for the first time. From the armored plates that lined its back, for example, he could figure out how slowly the crocodile grew.

The remains also shed light on the species' likely hunting techniques and suggest that Sarcosuchus was the biggest of the prehistoric crocodiles--twice the length of the largest modern crocs and up to 20 times as heavy.

"Sereno's specimens are adding a lot of information to the record of a creature that up until now has been very poorly known," said Wann Langston, a University of Texas paleontologist whose specialty is fossil crocodiles.

World-renowned for his dinosaur work, Sereno was so intrigued by the Sarcosuchus bones that he later went to swamps in India and Costa Rica to catch and study living but very distant crocodile cousins of Super Croc.

The crocodiles were surprisingly smart, he said.

"When we went to India to study and capture gharials [an Indian species], once they would get a sniff of us they became so cunning we hardly ever could find them," said Sereno. "You get the idea in zoos that they are static, mindless creatures. [But] they have a full range of behaviors and calls and actually participate in taking care of their young. They are cunning predators."

Crocodiles as a life form have been around even longer than dinosaurs. Other giant croc species that have populated the world's marshes include Deinosuchus in North America and Rhamphosuchus in what is now Pakistan. Those were both 35-footers.

"You wouldn't want to find any of them in your swimming pool," Langston said.

Sarcosuchus, which lived just before the ancestors of today's crocodile species emerged, came from a branch of ancient crocodiles that was lost with the great dinosaur die-off 65 million years ago.

Sereno said Sarcosuchus probably hunted much like modern crocodiles. It swam in immense rivers, 300 to 700 feet wide, that crisscrossed a rolling, lightly forested area of Africa that is now the Sahara.

The enormous reptile would have cruised near riverbanks, Sereno said, showing only its eyes and nostrils above water while it looked for unwary land animals feeding or drinking at the water's edge.

"It based its attack by exploding on the scene and grabbing furiously with its jaws," said Sereno. "It's a safe bet to say it was eating dinosaurs and anything else that came close to the water. The only land animals then to speak of were dinosaurs and turtles. It would have found smaller, young dinos fair game to hunt and eat."

Judging from its huge nose cavity, it also had an enhanced sense of smell that would have helped it find carcasses of dead dinosaurs to dine on.

Beyond its powerful jaws and tail, Sarcosuchus protected itself with 18-inch armored plates, called scutes, "laid down like roofing tiles" along its back, said Sereno.

"The scutes were a multipurpose physiological development serving to protect it from bites from its peers, and they also acted like radiators, transferring heat while it basked in the sun," Sereno said.

Though the Sarcosuchus skull retrieved by Sereno and his expedition crew was almost complete, they found only about 50 percent of its skeleton.

Using bones from several partial Sarcosuchus skeletons, Sereno is building a fleshed-out model of what it looked like. It will be displayed somewhere in Chicago early next year, he said, along with animatronic models of African dinosaurs he discovered earlier.

Dinosaurs and crocodiles are both reptiles, but physiologically they are very different animals, said Sereno.